The Colombo Stock Exchange ended Thursday's trading session with a slight decline, though shares of Industrial Asphalts (Ceylon) jumped sharply following news of an upcoming voluntary acquisition offer.

Sri Lanka's benchmark stock index retreated fractionally during Thursday trading, with the All Share Price Index declining 0.05 percent to close at 21,405.62 points. The more actively traded S&P SL20 index also fell marginally, dropping 0.02 percent to 6,019.25 points, according to CSE data.

Several stocks managed gains despite the overall downward movement. Aitken Spence, Dialog Axiata, Central Finance Company, and Commercial Development Company all posted increases, ranging from 0.43 to 2.71 percent. On the negative side, John Keells Holdings, Citizens Development Business Finance, and Digital Mobility Solutions Lanka led declines. Market activity remained relatively modest, with total turnover reaching 1.5 billion rupees, with the banking sector accounting for approximately 490.6 million rupees of trading volume.

Industrial Asphalts (Ceylon) emerged as a standout performer, with shares climbing 16.67 percent to close at 0.70 rupees. The sharp increase followed an announcement that Arcasia Investment & Trading and ATX Partners will launch a voluntary offer to acquire all ordinary shares in the company at 40 cents per share. The acquisition offer, commencing August 21, is scheduled to close on September 12 and would value the company's 3.75 billion shares at approximately 1.5 billion rupees under complete acceptance of the terms.